European Patent EP-B 763 262 discloses a filling apparatus for filling battery cells of the species indicated, in which apparatus the water is directed, behind the connector fitting, on a U-shaped upward path that acts as a siphon, to a spillover partition, from whence it travels through a lateral overflow channel under the open valve body.
A refilling plug of this kind, and plugs of similar design, serves for automatically refilling battery cells with distilled water. This is brought about in practical terms substantially using three different methods:
1. By means of gravity-fed water from a tank that is attached at a specific height above the battery to be filled. The outflow opening of the tank is connected via a quick-connect coupling to the filling system that is mounted above the battery surface, and the installed refilling plugs control water inflow into the battery cells via a valve-and-float system.
2. By means of a pump, which is often driven by a motor at low voltage (approx. 12 volts) and provides water from a tank at a pressure of approximately 0.5 to 1.0 bar. The outflow opening of the pump is connected by means of a quick-connect coupling to the filling system, which is mounted on the battery surface. Here as well, the installed filler plugs control water inflow into the battery cells via a valve-and-float system.
3. By means of tap water from the public water system. In this case the water pressure (approx. 4 bar) available from the public water system is used as filling pressure, and after prior preparation of the water by means of an ion exchanger, the water is connected via a quick-connect coupling to the filling system, which is mounted on the battery surface. A valve-and-float system controls water inflow through the filler plugs into the battery cells.
The above three examples indicate that a filling system must be used, and must function, under a wide variety of conditions. The object underlying the invention is therefore that of making available a water refilling plug that works reliably at all practically occurring pressures, so that it can be used without difficulty not only for very low filling pressures, but also for relatively high pressures.